1. Field of the Invention
The present invention relates to a semitransparent reflector. Precisely, the invention relates to a semitransparent reflector that transmits the light from a light source on the back side thereof and reflects the light from a light source on the front side thereof to thereby realize a high brightness.
2. Description of the Background
A display device is known, in which the built-in light source is switched on in the dark to visualize the display image by the action of the transmitted light, but is switched off in the light to visualize the display image by the action of the external reflected light. Its typical constitution is shown in FIG. 1, in which the back side of the liquid-crystal cell is specifically noted. The constitution is characterized in that a polarizer and a semitransparent reflector are laminated on the back side of the liquid-crystal cell in that order.
In the liquid-crystal unit of the type, the semitransparent reflector functions for efficiently utilizing the light from the built-in light source in the dark and the light from the external light source in the light both for displays, and also for realizing displays that meet various objects. In general, glaring transmitted light and reflected light are disliked. For increasing the display visibility, the transmittance and the reflectance of the semitransparent reflector must be well balanced, and the display device must have high transmittance and high reflectance.
Heretofore, a semitransparent reflector fabricated by forming a coating layer with a filler such as pearl pigment, silica, alumina or the like therein on a transparent or opacity-controlled base film is used, and its whole light transmittance T and whole light reflectance R are specifically controlled. Also known is a technique of adding the same type of filler as above to the adhesive for bonding a polarizer and a semitransparent reflector to thereby specifically control the whole light transmittance T and the while light reflectance R of the reflector.
These semitransparent reflectors that have heretofore been known may enjoy the balance between the brightness from the transmitted light and the brightness from the reflected light, but could not often attain the intended transmission and reflection brightness in display devices, depending on the optical properties of the constituent components.
The present invention is to attain efficient light transmission and reflection in a display device with a semitransparent reflector installed therein, and to attain a high transmittance and a high reflectance of the display device so as to significantly improve the letter visibility of the device.